• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.115-118
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• 2002

The present study deals with CFD analysis of a plastic heat exchanger with corrugated wall. This exchanger has sinusoidal corrugations, and the flow through the exchanger is three dimensional. In addition, CFX-5.4, a commercial code utilizing unstructured mesh, was used as a computational method for solving RANS(Reynolds-Averaged Navier-Stokes) equations, and the applied turbulence model is $k-{\varepsilon}$ model. The factors to affect the efficiency of a plastic heat exchanger are heat conductivity, flow characteristics and so on. For those two factors, heat conductivity is fixed by the wall material. Therefore, the How along the corrugation affects the efficiency more, provided the same material. In conclusion, the heat transfer enhancement of a plastic heat exchanger with corrugated wall can be recognized from the flow characteristics such as velocity streamline, local heat transfer coefficient, velocity contour, and pressure contour. To confirm the results, both of the measured and the computational data for pressure loss were compared with each other, and they were identical.

• 한국분무공학회지
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• 제15권4호
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• pp.202-207
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• 2010

Mist cooling is widely employed as a cooling technique of high temperature surfaces, and it has heat transfer characteristics similar to boiling heat transfer which has the convection, nucleate and film boiling regions. In the present study, mist cooling heat transfer was experimentally investigated for the mist flow impacting on the heated surfaces of mico-fins. The mist flow was generated by supersonic vibration. Experiments were conducted under the test conditions of droplet flow rate, $Q=6.02{\times}10^{-9}{\sim}3.47{\times}10^{-8}\;m^3/s$ and liquid temperature, $T_f=30{\sim}35^{\circ}C$. From the experimental results, it is found that an increase in the droplet flow rate improves mist cooling heat transfer in the both case of smooth surface and surfaces of micro-fins. Micro-fins surfaces enhance the mist cooling heat transfer. Besides, the experimental results show that an increase in the droplet flow rate decrease the heat transfer efficiency of mist cooling.

• Membrane and Water Treatment
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• 제10권5호
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• pp.387-394
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• 2019

Membrane distillation (MD) is one of the water treatment processes which involves the momentum, heat and mass transfer through channels and membrane. In this study, CFD modeling has been used to simulate the heat and mass transfer in the direct contact membrane distillation (DCMD). Also, the effect of operating parameters on the water flux is investigated. The result shows a good agreement with the experimental result. Results indicated that, while feed temperature is increasing in the feed side, water flux improves in the permeate side. Since higher velocity leads to the higher mixing and turbulence in the feed channel, water flux rises due to this increase in the feed velocity. Moreover, results revealed that temperature polarization coefficient is rising as flow rate (velocity) increases and it is decreasing while the feed temperature increases. Lastly, the thermal efficiency of direct contact membrane distillation is defined, and results confirm that thermal efficiency improves while feed temperature increases. Also, flow rate increment results in enhancement of thermal efficiency.

• 설비공학논문집
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• 제27권3호
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• pp.146-151
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• 2015

The heat transfer performance of heating medium oil fluidized bed heat exchanger was measured. The operation variables were air flow rate, air inlet temperature, moisture content, water flow rate and water inlet temperature. The outside heat transfer coefficient was determined from the heat exchanger experiment and its experimental correlation was determined as a function of air velocity and viscosity of heating medium oil. Effect of viscosity was well agreed with the previous studies. Errors of the correlation equation was less than about 10% for outside heat transfer coefficient developed in this study when compared with the measured value. Hot water with the temperature greater than $77^{\circ}C$ could be produced by using the heating medium oil fluidized bed heat exchanger.

• Journal of Advanced Marine Engineering and Technology
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• 제23권5호
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• pp.687-694
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• 1999

This study was conducted to develop new drying process for automatic control and marine engi-neering system. Air-water tests were carried out to investigate dryer performance. The dispersed flow in he dryer test apparatuses was also simulated by using a numerical code which solves the Dittus-Boelter equation for continuous liquid phase and the Reynolds equation of droplet motion for continuous liquid phase and the Reynolds equation of droplet motion for dispersed phase to predict droplet removal efficiency. Proper conditions for dehumidification were optimized by response ambient conditions. When the selected indexes were constrained in the range of 85-98% moisture content above $15^{\circ}$ and more than mass flow rates of moist air 750kg/h. The numerical results were compared with the experimental data pertaining to the removal effi-ciency at chamber stage and overall pressure drop along concentric tubes Good agreement was obtained as for the efficiency while relatively poor agreement was obtained for the relative humidity. The results also showed that the efficiency depended strongly on the relative humidity at the inlet condition which indicated the importance of estimating the heat exchanger length. Effects of some design parameters in both removal efficiency and breakthrough onset condition are discussed.

• 설비공학논문집
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• 제13권7호
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• pp.549-556
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• 2001

Heat flow characteristics during hot water extraction process was studied experimentally. Data were taken at various outlet port type for the fixed inlet port type, inlet-outlet temperature differences and mass flow rates. In this study, the temperature distribution in a storage tank and an outlet temperature were measured to predict a flow pattern in the storage tank, and a hot water extraction efficiency was analysed with respect to the variables dominating a extraction process. Experimental results show that the extraction efficiency is high in a low flow rate in case of using modified distributor I(MDI) as a outlet port type.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2003년도 추계 학술발표회 논문집
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• pp.299-304
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• 2003

Heat regenerator occupied by regenerative materials improves thermal efficiency of regenerative combustion system through the recovery of sensible heat of exhaust gases. By using one-dimensional two-phase fluid dynamics model, the unsteady thermal flow of regenerators with spherical particles were numerically analyzed to evaluate performance of ratio of waste heat recovery and temperature efficiency and to suggest optimized conditions of heat regenerator. It is predicted that exhaust gases temperature at regenerator outlet of 3.5$\times$10$^{6}$ kcal/hr heat regenerator is even lower than design condition and ratio of waste heat recovery is 75.8％.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.183-189
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• 2004

The flow and the heat transfer about the cross-flow fin-tube heat exchanger in an out-door unit of a heat pump system has been numerically Investigated. Using the general purpose analysis code, FLUENT, the Navier-Stokes equations and the energy equation are solved for the three dimensional computation domain that encompasses multiple rows of the fin-tube. The temperature on the fin and tube surface is assumed constant but compensated later through the fin efficiency when predicting the heat-transfer rate. The contact resistance is also taken into consideration. The flow and temperature fields for a wide range of inlet velocity and fin-tube arrangements are examined and the results are presented in the paper. The details of the flow are very well captured and the heat transfer rate for a range of inlet velocity is in excellent agreement with the measured data. The flow solution provides the effective permeability and the inertial resistance factor of the heat exchanger if the exchanger were to be approximated by the porous medium. This information is essential in carrying out the global flow field calculation which, in turn, provides the inlet velocity lot the microscopic temperature-field calculation of the heat exchanger unit.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1995년도 춘계학술발표회 초록집
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• pp.69-76
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• 1995

The horizontal thermal storage tank with heat pipe which is suitable for the sensible heat storage system is able to store a hot water from the heat source such as heating pad efficiently and to supply a hot water to load rapidly. Therefore Arrangement of heating pad affects thermal flow and thermal storage efficiency. So, if effective arrangement is decided for condition of constant number of heating pad, the more rapid thermal flow effect and higher thermal storage efficiency is obtainable by active heat transfer. In this experiments, number of heating pad is ranged from three, five and nine, and when number of heating pad is constant, arrangement are two types of concentration-type and dispersion-type. As a result, for the case of concentration-type of heating pad, strong entrainment take place in horizontal thermal storage tank with heat pipe by active heat transfer and in the constant number of heating pad, the concentration-type has the higher efficiency with about 5∼6% than the dispersion-type. Therefore, when heating pad is equipted to horizontal thermal storage tank with heat pipe, concentration-type of heating pad is an efficient design in constant number. of heating pad.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4302-4307
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• 2011

최근에 연비향상을 위해 다양한 기술들이 개발 중에 있다. 본 연구의 목적은 배기열 재순환장치의 열교환 성능을 평가한 후 최적 성능의 모델을 제안하는데 있다. 이 장치는 버려지는 배기열을 이용하여 가능한 한 빠르게 엔진 냉각수를 웜업 시키도록 설계하였다. 이 목적을 달성하기 위하여 CFD를 이용하여 냉각수의 흐름 방향과 냉각수의 유입 유출 위치에 따른 열유동 특성을 분석하고, 열교환 효율을 상승시키기 위한 방법을 제시하였다. 그 결과 냉각수 유량이 적고, 배기가스와 냉각수의 유로를 각각 구성하여 배기가스의 열이 직접적으로 냉각수에 영향을 미치는 구조가 가장 열교환 효율이 좋은 것으로 나타났다.